NZ205146A - Preparation of vesiculated granules of crosslinked carboxylated polyester resin - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £05146 205146 Priority Date(s): /.Q.. ?.. .. P. (. . & Complete Specification Filed: Class: <?>%?>./?.<.. .C £ 3 JAN 1337 Publication Date: ' P.O. Journal, No: .... I.t\ !^'/. 1 kS ^ NEW ZEALAND No.: Date: PATENTS ACT, 1953 COMPLETE SPECIFICATION PROCESS OF PREPARING VESICULATED POLYESTER GRANULES K/We, DULUX AUSTRALIA LIMITED, a company incorporated under the laws of the State of Victoria of 35 Collins Street, Melbourne, Victoria 3000, Australia hereby declare the invention for which X/ we pray that a patent may be granted toXHK/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - * (followed by page la) 205146 PROCESS OF PREPARING 75SICULATED POLHrSJEn ■CnAMULEB Thl3 invention relates to vesiculated polyester granules and more particularly to a process of preparing such granules. It is known that vesiculated granules 5 of carboxylated unsaturated polyester crosslinked with ethylenically-unsaturated monomer can confer advantageous properties on coating compositions in which they are incorporated, and as a result there has been extensive usage of such granules in a variety 10 of applications. The background to the subject is well covered in the literature, for example, in articles by Kershaw (Australian OCCA Proceedings and News, 8 No.8, 4 (1971)), Lubbock (Australian OCCA Proceedings and News, 11, No.5, 12 (197*0), Hislop 15 ana McGinley (Journal of Coatings Technology, 50 (642), 69 (1978)), and Bierwagen (Congress Book of the XVth ?ATIPEC Congress, 3E-Activities, Vol.Ill, 110 (1980)). A number of patents relating to these granules and their use in coating compositions have 20 also issued, these including New Zealand Patents Nos. 162303, 172371, 162156, 175509, 158419, 167461 and 195624.

The preferred process of preparation of such granules is now well established. It is a "double 25 emulsion" process wherein water is first stably dispersed in a solution in polymerisable monomer of a carboxylated unsaturated polyester to give a "first emulsion" and the first emulsion is itself stably ^ ^ T i'v dispersed in water to give a "double emulsion". 205146 m o 20 © O 25 Free radical polymerisation is then initiated to give vesiculated granules of crosslinked polyester resin. If pigmented vesiculated granules are required, pigment may be dispersed in either or both of the first emulsion components using conventional pigment dispersants.

The state of the art in granule technology is represented by the "dimensionally stable" vesiculated granules of Gunning, Henshaw and Lubbock (NZ 172371), the improved process of preparing such granules of Gunning and Lubbock (NZ 175509) and the process of Beresford and Braun (NZ 195624) wherein the inventors demonstrate the achievement of dimensional stability without the need for the polyamine bases of Gunning. In this last-named patent, the polyamine required for stabilisation of the first emulsion was replaced by an oxide, hydroxide or weak acid salt of a selected metal cation; in this way, the odour and yellowing effects of the polyamine could be considerably reduced (these granules shall hereinafter be referred to as "oxide granules"). Both of these types of granules have been used successfully in coating compositions.

However, it has sometimes been found that when oxide granules are prepared on a large scale, there is an unacceptably high incidence of "grit" particles, that is, aggregates of two or more granules which are formed 205146 o Is the coming together and partial coalescence of individual granules prior to curing; on polymerisation initiation, they fuse to give "grit" particles.

These particles may be visible to the naked eye and their presence In coating compositions Is highly undesirable as they appear as visible imperfections In the film.

We have now found that it is possible to reduce considerably and often completely eradicate the incidence of grit In oxide granules. Further, we have found that it Is possible to achieve with both oxide and polyamine granules opacities which are consistently higher than those previously attained.

We therefore provide, according to the present invention, a process of preparing vesiculated granules of crosslinked carboxylated polyester resin by a process comprising the steps of (a) forming a dispersion of particles of a solution of a carboxylated unsaturated polyester resin of acid value of frcm 5-50 mg.KCH/g in ethylenically unsaturated monomer, the solution also containing water droplets which are dispersed in the presence of a base selected from (i) a water-soluble polyamine which contains at least three amine groups per molecule and which has a dissociation constant (pKa value) of 9-5-10.5; and (ii) a metal oxide, hydroxide or salt wherein the metal cation is chosen from the group consisting: of calcium, magnesium, barium, titanium ■S. I ' •' ■* J- - -S. - J.-.;/.- lead, strontium and cobalt, the salt being one wherein the pKa value of the conjugate acid of the anion is greater than 2; the dispersion additionally containing a surfactant, 5 and (b) initiating free radical polymerisation to crosslink the polyester and monomer and give crosslinked, vesiculated granules, characterised in that (c) where a water-soluble polyamine is used, there 10 are present from 0.3-4.0 amine groups per polyester carboxyl group; (d) where a metal oxide, hydroxide or salt is used, there is present from 0.8-1.8 equivalents of metal cation per equivalent of polyester carboxyl group; and (e) the surfactant comprises a species of the formula ca^2a+l where a is 5-12; where R Is an alkylene oxide chain having from 2-12 alkylene oxide units selected from ethylene oxide, propylene oxide and butylene oxide, the units being selected such that when there is present in the chain alkylene oxide which is not ethylene oxide, such alkylene oxide shall comprise on average a maximum of two units per chain and such chain shall additionally comprise on average at least 3 ethylene oxide units; and where X is an anion having pKi of less than 2. 2 n : Carboxylated unsaturated polyester resins which will crosslink by reaction with unsaturated monomers are well known. Suitable polyester resins are the condensation products of dicarboxylic acids (or 5 their corresponding anhydrides) and dihydric alcohols, polymerlsabie unsaturation being introduced into the chain by the use of a proportion of **< 3p -ethylenically unsaturated acid.

The polyester resins from which a selection is 10 made are condensation products of polybasic acids (or the corresponding anhydrides) and dihydric alcohols. Polymerlsabie unsaturation is introduced into the molecule by the selection of an o< ,^j-ethylenically unsaturated acid, optionally in combination with a 15 saturated" acid or anhydride.

Thus suitable acids are, for example: unsaturated aliphatic acids, e.g. maleic, fumaric and itaconic acids; saturated aliphatic acids, e.g. malonic, succinic, glutaric, adipic, pimelic, azelaic, tetrahydrophthalic, chlorendic and sebacic acids; and saturated aromatic acids, e.g. phthalic, isophthalic, terephthalic, tetra-25 chlorophthalic, trimellitic and trimesic.

Suitable dihydric alcohols are chosen from, for example, ethylene glycol, poly(ethylene glycols) e.g. diethylene glycol, hexane 1, 6-diol, propylene glycol, di-cyclohexanol and neopentyl glycol. Alternatively, the alcohol may be one which initially contained three or more hydroxyl groups, the groups in excess of two optionally being at least In part etherified with, for example, a monohydric alcohol e.g. methanol, ethanol and n-butanol or esterified with a monobasic acid, e.g. benzoic acid, p-tert.-butyl benzoic acid and chain-like aliphatic acids of up to 18 carbons atoms chain length e.g. coconut oil monoglyceride.

The methods by which unsaturated polyesters of this type are formulated and made are well known in the art.

It is essential to the working of our invention that the acid value of the polyester lie within certain limits. We have found it essential to select polyesters whose acid values lie In the range 5-50 mg KOH/g, preferably 10-25 mg KOH/g and most preferably 15-20 mg KOH/g.

The unsaturated monomer in which the unsaturated polyester resin is dissolved and crosslinked must be essentially water-Insoluble. Monomers which have a solubility at 20°C of less than 5% (w/w) in water are considered to be suitably water-insoluble for our purpose. A single monomer or a mixture of monomers may be used and In general the monomer will contain only a single polymerlsabie double bond.

However, it is known that polyfunctional monomers, that is, monomers containing more than one polymerisable double bond, may also be used to cross-link unsaturated polyester resins. Such polyfunctional monomers 'are, 5 however, normally present only as a minor constituent of a mixture of monomers, the major proportion of which is monofunctional monomer. Hence mixtures comprising e.g. divinyl benzene may be used in the performance of our invention.

The preferred ethylenicaliy unsaturated monomers for general use in our process are selected from styrene, the mixed isomers of methyl styrene commercially available as 'vinyl toluene' and methyl methacrylate, because of the ease with 15 which they can be copolymerised with the unsaturated polyester resin. For the best results, we prefer that the monomer shall comprise at least 50% by weight of styrene.

The choice of monomer is not, however, restricted 20 to the above monomers alone. Bearing in mind the requirements that the total monomer must be essentially insoluble In water and also be a solvent for the unsaturated polyester resin, there may be present in a minor proportion other polymerisable unsaturated 25 monomers to, for example, modify the physical properties of the coreacted resins. Typical co-monomers are, for example, ethyl acr.ylate, n-butyl methacrylate, acrylonitrile, and triallyl cyanurate. In general, we 205146 have found that the upper limit of usefulness of such monomers is 10% by weight based on the total monomer used. Higher concentrations give granules which are either too brittle or too rubbery to be used 5 effectively in paints.

Optionally a few percent by weight of a non-polymerising organic liquid, e.g. n-butanol or toluene, may be mixed with the monomer to increase the solubility of the polyester resin therein or may be Introduced as 10 an Incidental part of the process, e.g. in preparing the polyester.

There is included in the dispersions according to our invention a surfactant which comprises a species of the formula ^5 CaH2a+i ^o>—■ where a, R and X have the meanings described hereinabove. < v A. r The species should preferably have the formula . where a is 5-12 and b is 2-11. The anion X may be selected from any suitable anion and such anions as sulphate and maleate may be used. Typical examples of suitable species are the sulphates of nonylphenol and dodecylphenol ethoxylates wherein the 25 the alkylene oxide chain comprises at least 5 ethylene oxide units.

When only ethylene oxide Is present in the alkylene oxide chain, the number b may be as low as two, but when other alkylene oxides are present, the minimum 205146 number of ethylene oxide units Is three. Furthermore, the other alkylene oxide must not comprise more than two units per alkylene oxide chain on average.

A counter ion for the species shown above may 5 be selected from any suitable materials. Naturally, it is preferable to avoid those which confer deleterious properties; for example, some metal cations can impart quite strong colours and some organic cations confer strong odours. Counter ions 10 which are suitable for use in our invention are, for example, Mg2+ and K+, NH^+ being an especially preferred counter ion.

The surfactant is typically present to the extent of from 0.75-7.5# (preferably 3-0 - U.5%) by weight 15 of dispersant solids per volume of total granule solids and may be added initially to any of the phases of the dispersion prior to polymerisation.

The base used in this invention may be selected from the polyamine bases of the variety described by 20 Gunning in New Zealand Patents No. 172371 and 175509 or the metal oxide, hydroxide and salt J?'9' bases described by Eeresford in New Zealand Patent n ^ No. 195624, the disclosures of these documents being Incorporated herein by reference. We have 25 found that for our purposes the best base Is magnesium oxide. When an amine base is used, sufficient amine should be present such that there are present from 0.3-4.0, preferably 1.3-3.2 amine groups per polyester 205146 carboxyl group. When a metal oxide, hydroxide or salt base Is used, sufficient base should be present such that there Is present from 0.8-1.8 equivalents of metal cation per equivalent of polyester carboxyl group.

When pigmented granules are desired, the pigment may be selected from any suitable pigment known to the art. We have found that commercial enamel grades of rutile titanium dioxide are the best pigments for our purposes. A large number of these are 10 available and their suitability for use in our process varies according to the nature and size of the coating on the pigment particles. The most suitable pigments for use in a given formulation are best determined by trial and error. It is permissible to use other 15 primary pigments and extenders such as calcite and barytes.

Our preferred method of preparation of granules is the "double emulsion" method referred to hereinabove. A process of preparing unpigmented vesiculated granules A T in a "single emulsion" is known. In this process, described by Gillan and Kershaw in New Zealand (\ 1 r\* Patent No. 162303, a carboxylated unsaturated '* polyester resin is dispersed in water and polymerlsea^^.y^..'^ the vesicles forming spontaneously within the dispersed 25 resin globules. It was thought, however, that where pigmentation of the granules was desired, a double emulsion process was still essential for optimum vesiculation and pigment dispersion and utilisation. 20S146 O o We have now found that our process allows us In some circumstances to prepare pigmented vesiculated granules using a single emulsion process. This option is a potentially very valuable one as it offers reduced 5 production times and increased convenience of handling.

The Initial stage in the preparation of dimensionally stable granules according to the present invention by the "double emulsion" process is the emulsification of water into the solution in ethylenically unsaturated 10 monomer of carboxylated unsaturated polyester resin (the solution in ethylenically unsaturated monomer of carboxylated unsaturated polyester resin shall hereinafter be referred to as "the polyester solution" and the emulsion of water in the polyester solution shall 15 hereinafter be referred to as "the first emulsion").

This Is carried out by mechanical agitation which is continued until the viscosity of the emulsion is essentially constant. We have found that, during this stage, it is essential that the rate of agitation ,-/"v A 1 ^ be carefully regulated. The maximum rate of agitation depends on the particular formulation and /Q^q the type of agitation used, but as a general guide, we find that for impeller-type agitators, the maximum permissible impeller tip speed is about 10 metres per 25 second. This speed is somewhat lower than the 15 metres per second disclosed by Gunning in NZ 175509, but we have found that for the purposes of t'ni3 invention, tip speeds in excess of about 10 metres per second result in inferior granules. We prefer to keep —... I & a ■O 2 514 6 the tip speed below about 8 metres per second. The agitation is carried out in the presence of the base which may be present in the polyester solution, the water or both. If pigmented granules are required, 5 the pigment may be added at this stage, or it may be added to the water, the polyester solution or both prior to the formation of the first emulsion.

The first emulsion is dispersed in water which contains a stabiliser for the dispersed first emulsion 10 particles and stirred until the desired granule size is achieved; this is the "double emulsion". The stabiliser may be chosen from the wide range of materials known to be suitable for this purpose but we have found that an especially suitable material is 15 a water-soluble partially hydrolysed poly(vinyl acetate) with a molecular weight of about 100,000 and a degree of hydrolysis of 85-90$. As a general guide, we have found that a concentration of stabiliser of the order of 0.1-2.0? by weight of the total water (vesicular 20 water & continuous phase water) gives satisfactory results. The surfactant may be added at any stage of the process prior to polymerisation and to any phase of the double emulsion.

An increase in the viscosity of the water can often & 25 assist in the dispersion of the emulsion; such an increase can be achieved by the addition to the water of a water-soluble polymeric thickener. Suitable thickeners are well known to the art and include such m 205146 © compounds as hydroxyethyl cellulose, typically used at a concentration of about 0.1-0.5% by -weight of the continuous water phase.

Polymerisation of the polyester resin is effected by free radical means. This can be achieved by the use of a free radical initiator such as an organic peroxide or by exposure to a radiation source such as ultra-violet radiation or a radio-active element.

When a free radical initiator is used it may be 10 conveniently dissolved in the polyester resin solution before the dispersion of the solution in water or it may be added to the continuous water phase following the formation of the double emulsion.

Our preferred initiation system Is a redox system of 15 diethylene triamine and curnene hydroperoxide triggered by ferrous ions derived from ferrous sulphate. These three materials are added sequentially to the continuous phase of the double emulsion.

The aqueous slurry of vesiculated polyester granules 20 thus formed may be used directly in an aqueous latex paint, or it may be dewatered, by any convenient means, for example the method described in i ii uNq.

New Zealand Patent No. 187768, and subsequently \\ redispersed In an aqueous or non-aqueous medium, or Incorporated into a paste, for example, for use as a filler or a putty.

The paint compositions prepared using granules according to our process are consistently more 2 v - I 4 6 opaque than otherwise identical compositions comprising granules known to the art; this difference is especially marked in paint compositions with a high pigment volume concentration (PVC). It is a notable fact that even unpigmented granules prepared according to this invention confer a degree of whiteness and opacity previously conferred only by pigmented granules.

These granules offer the paint technologist considerable formulation latitude; he can, for example, maintain a given paint formulation at an acceptable opacity whilst effecting considerable cost savings, or he can achieve a very high degree of opacity and whiteness at no extra cost. In addition, those paints utilising oxide granules have few of the unsightly aggregates which marred the appearance of paints utilising known oxide granules.

The invention is further described with reference to the following examples in which all parts are expressed by weight.

EXAMPLE 1 Preparation of 10 um pigmented vesiculated polyester resin granules in which the first step involves dispersing the pigment in the resin phase. n n ■ 'A Parts A polyester resin 1 2.715 styrene 1.205 B titanium dioxide pigment 10.015 ("Tipure"* R902 ex DuPont USA) C polyester resin 5.495 styrene 3-349 D magnesium oxide 0.045 E water 9.028 surfactant 2 0.664 antifoam ("Foamaster"* NS1 ex Diamond 0.015 Shamrock Corp.) F water 30.779 poly(vinyl alcohol) solution 3 5.837 G water 30.271 ferrous sulphate 0.003 diethylene triamine 0.045 H cumene hydroperoxide^ 0.087 I bactericide ("Proxel"* PL ex ICI 0.047 Australia Ltd.) 37% ammonia solution 0.400 100.000 1.

A 65$ weight solids solution of a 2.34/0.912/3.74 (molar) maleic anhydride/phthalic anhydride/propylene glycol polyester In styrene was used. 16 - 1 A f> 2. An 83% weight solids solution of ammonium nonylphenol ethoxylate sulphate was used - the compound had five ethoxy units. 3. A 7.5% weight solids aqueous solution of "Foval"* 4. A commercially available 90% weight active ingredient was used. to A with stirring to form a millbase. Stirring was continued at high speed until the pigment was completely dispersed and the materials C were then mixed and added to the millbase. The magnesium oxide D was then added to the mixture and stirring was continued until 15 the magnesium oxide was completely dispersed.

The materials E were mixed until homogeneous and then added to the mixture of materials A-D and stirred in to form a water-in-oil emulsion. This was the "first emulsion".

The materials F were blended together and the first emulsion added to the blend under vigorous stirring, the stirring being continued until the globules of first emulsion were about 10 um in diameter; this was the "double emulsion". All the water, ferrous sulphate 25 (dissolved In a little water) and diethylene triamine (materials G) were then added to the double emulsion. The cumene hydroperoxide H was stirred in and the mixture allowed to cure overnight. 224 (ex Kuraray Rayon) was used. * trade mark: The materials A were mixed and the pigment B added Finally, the bactericide (I) was added with stirring and the pH of the mixture adjusted to 8.5-9.5 with ammonia solution.

The final product was a 23% weight solids slurry of crosslinked polyester resin granules of 10 um maximum diameter; the slurry being free of "grit" particles. These were tested for shrinkage by the method of USP 3,879,314 and were found to have a shrinkage of less than 5%- EXAMPLE 2 Use of a number of different surfactants.

Example 1 was repeated except that the surfactant was replaced in turn by the following; (a) ammonium nonylphenol alkoxylate sulphate, wherein the alkoxylate comprises one propylene oxide and five ethylene oxide units, the propylene oxide unit being adjacent to the phenol group; (b) as (a) but with the propylene oxide unit replaced by a butylene oxide unit; (c) as (b) but with the butylene oxide unit at the end of the alkoxy chain remote from the phenol group; (d) magnesium nonylphenol ethoxylate sulphate, the ethoxylate chain having five ethylene oxide units; and (e) ammonium dodecylphenol ethoxylate sulphate, the ethoxylate chain having five ethylene oxide units.

Claims (12)

© - 18 - i All of these preprations gave crosslinked polyester resin granules of 10 um maximum diameter and with shrinkage of less than 5%. All of the slurries were free from "grit" particles. EXAMPLE 3 (^ 5 Use of a polyester outside the preferred acid value range. Example 1 was repeated except that the polyester resin of that example was replaced by on with an acid value of 28 (I.e. outside the preferred range of 10-25). 10 The preparation gave a slurry of crosslinked polyester resin granules which had a shrinkage of less than 5% but which were slightly less opaque than those of Example 1. The slurry was free from "grit" particles. EXAMPLE 4 15 Use of an amine base. Example 1 was repeated except that the 0.045 parts of magnesium oxide (Stage D) were replaced by 0.140 parts of diethylene triamine and 0.043 parts of monoisopropanolamine, and the surfactant level In Stage 20 E was reduced from 0.664 parts to 0.445 parts. The preparation gave a slurry of vesiculated polyester resin granules of shrinkage less than 5% but opacity slightly lower than that of the granules of Example 1. The slurry was free from "grit" particles. O 205146 Vjlr\0i/^ . — 19 — ■fThl*. P. 1 a-1 I'll n riinf-fn4-ng thjP 1mrnn<-^n or>o go Pn-|-|nwn.

1. A process of preparing vesiculated granules of crosslinked carboxylated polyester resin by a process comprising the steps of (a) forming a dispersion of 5 particles of a solution of a carboxylated unsaturated polyester resin of acic value of frcm 5-50 mg.KOH/g in ethylenically unsaturated rtoncner, the solution also containing water droplets which are dispersed In the presence of a base selected from 10 (i) a water-soluble polyamine which contains at least three amine groups per molecule and which has a dissociation constant (pXa value) of 9.5-10.5; and (11) a metal oxide, hydroxide or salt wherein the 15 metal cation is chosen from the group consisting of calcium, magnesium, .barium, titanium, zinc, lead, strontium and cobalt, the salt being one wherein the pKa value of the conjugate acid of the anion is greater than 2; 20 the dispersion additionally containing a surfactant, and (b) initiating free radical polymerisation to crosslink the polyester and monomer and give crosslinked, //'V vesiculated granules, characterised in that (c) where a water-soluble polyamine is used, there 25 are present from 0.3-4.0 amine groups per polyester^\;;>£. carboxyl group; (d) where a metal oxide, hydroxide or salt is used, there Is present from 0.8-1.8 equivalents of metal cation per equivalent of polyester carboxyl group; and 20 205140 (e) the surfactant comprises a species of the formula where a is 5-12; where R is an alkylene oxide chain having from 2-12 alkylene oxide units selected from ethylene oxide, propylene oxide and butylene oxide, the units being selected such that when there is present in the chain alkylene oxide which is not ethylene oxide, such alkylene oxide chain shall comprise on average a maximum of two units per chain and such chain shall additionally comprise on average at least 3 ethylene oxide units; and where X is an anion having a pK^ of less than 2.

2. A process according to claim 1 characterised In that the surfactant comprises a species of the formula where a is 5-12 and b is 2-11, and X is as defined in claim 1.

3. A process according to claim 1, characterised in that the anion is selected frcm sulphate and maleate-

4. A process according to claim 1, characterised in that the counter ion for the species Is selected from NH4+, Mg2+ and K+.

5. A process according to claim 1 characterised in that the acid value of the polyester is from 10-25 nigr-^^p KOH/g. Ca^2a+1 205146 - 21 -

6. A process according to claim 1 characterised in that said dispersion of particles of solution is formed by the steps of (a) dispersing water in a solution,in ethylenically unsaturated monomer, of a carboxylated unsaturated polyester resin to give a first emulsion; and (b) dispersing the first emulsion in water to give the • dispersion of particles of solution.

7. A process according to claim 6 characterised in that the dispersion is carried out by stirring and that/ during the formation of the first emulsion, the rate of agitation is such that the tip speed of the stirrer does not exceed 10 metres/second.

8. A process according to claim 7 characterised in that the tip speed of the stirrer does not exceed 8 metres/second.

9. A process according to claim 1 characterised in that said dispersion of particles of solution is formed in a single process.

10. A process according to claim 9 characterised in that the dispersion is formed by stirring and that the tip speed of the stirrer does not exceed 10 metres/second.

11. A process according to claim 9 characterised in that the dispersion is formed by stirring and that the tip speed of the stirrer does not exceed 8 metres/second.

12. A process according to claim 1 substantially as described with reference to the examples. By -Wi^yTheir authorised Agent A. J. PARK & SON: Per;